Engine tuning help

[Jim's cart]

Hi, I am new to the group. I have a homemade go-cart I have made for my boys to ride around our yard. I have put a 49cc engine onto it but am having trouble getting it to fully rev out, no matter how I adjust mixture screw on carby. It is the 49cc "race engine", I have put a performance exhaust on it. If I go over about 3/4 throttle it bogs down. Can anyone offer any suggestions??

 

[Doc Sprocket]

Perhaps the new exhaust is so free-flowing that now you need to rejet. What's the plug look like? Welcome to the forum!

 

[OzFab]

dual posts & all

Can we assume the engine is 2 stroke? If so, most small 2 stroke carbs have high & low mixture adjustments; have you tried tweaking both?

 

[Jim's cart]

The plug was looking very brown and dry, so I have increased the oil in fuel mixture, I think a little too much as it is blowing a fair bit of smoke at the moment. The carby only has one mixture screw and I have tried just about everywhere to get it to rev.

 

[DS13]

Have ya cleaned the carb?

 

[Jim's cart]

I haven't cleaned the carby as the engine has only done about 4 hours running. I have had the fuel bowl off the carby and there wasn't anything in it.

 

[Clone]

Did it run better before and now your having this problem?

Sent from my HTC One S using Tapatalk 2

 

[DS13]

I haven't cleaned the carby as the engine has only done about 4 hours running. I have had the fuel bowl off the carby and there wasn't anything in it.

I'm assuming its a new engine then..

If not try taking the entire carb off and clean, it never hurts to clean, and is it jetted correctly?

 

[Jim's cart]

It is only a new engine, so i assume it is jetted correctly. I really haven't been able to get it to run yet, it would do a few laps of the house and then it seemed to be bogging down until it stopped. This was during some 40 degree days, so I thought it was something to do with the high ambient temp plus the heat developed from the engine. If I left it for half an hour it would start but again it would not last long. The days are a bit cooler now, but the engine still developes a lot of heat. It had a blue anodized head on it that the heat has discolored. I have suspicion on the fuel I was using, so I will try new fuel and a new mix of oil and try again.

 

[miamieddie]

Check ur plug on the color, if ok then it may need valve adjustment...Eddie

 

[Jim's cart]

The plug looks good. I made up new fuel today and it went well for about twenty minutes, then it seemed to run out of fuel and would not start. Does a fuel vapor lock seem possible? The engine gets very hot for only twenty minutes of run time.

 

[slipknot23]

how about some pics of the motor

 

[Jim's cart]

I have not worked out how to add pics yet. I had it running this morning for five minutes, if that and idling mainly, no load at all, and the engine was very hot again.